1. Field of the Invention
The present invention relates to an apparatus for analyzing blood in a non-invasive manner. More particularly, it relates to an apparatus for optically measuring blood flowing through a living body in order to analyze blood components required for a hematology test.
2. Description of the Prior Art
Hematology tests such as blood cell counting (white blood cell: WBC, red blood cell: RBC, etc), hematocrit (HCT), hemoglobin (HGB), and mean corpuscular constant (mean corpuscular volume: MCV, mean corpuscular hemoglobin: MCH, and mean corpuscular hemoglobin concentration: MCHC) are extremely important for the diagnosis of diseases and the treatment thereof. Such items are most frequently used during the clinical testing of patients.
Such hematology tests involve collecting blood from a patient to analyze the sample thereof with an analyzer. However, the collection of blood from a patient can cause considerable pain to some people. Since a hematology test on the collected blood is not a real-time test, the test result may not provide an accurate diagnosis. In addition, the above hematology test is always accompanied by a fear that needles used for blood collection may be used mistakenly after they have been used for collecting blood from someone who has contracted an infectious disease such as hepatitis or HIV. Thus, there has been a demand for many years for an apparatus that allows practitioners to perform a blood test in a non-invasive manner. When such a blood analyzer is installed beside the patient's bed, practitioners can monitor the patient's conditions on the spot without difficulty. As a prior art relating to such apparatus, a video microscope (for example, as disclosed in Japanese Published Unexamined Patent Application No. HEI 4(1992)-161915) is known which applies light to a portion of a patient's skin in order to photograph a video image thereof (static image) at a shutter speed of about one-thousandth of a second and identifies a discontinuous point in the blood stream where a point moves one by one in a static image. U.S. Pat. No. 4,998,533 (Winkelman) describes an apparatus and method for in vivo determination of red and white blood cell characteristics from a flow of red and white cells in mucous membranes, in which an image capturing device is employed to optically isolate images from a flow of blood cells and transmit those images to an image receiving device for encoding into electronic signals.
In addition, when the blood flowing through blood vessels of a patient are photographed with a conventional video microscope and a dynamic image thereof is observed, cubic and transparent objects such as white blood cells (leukocytes) can be recognized. This may be because the peripheries of the white blood cells have been made conspicuous against the static background.
However, observation of the static image of white blood cells cannot provide a clear particle image because of the virtual absence of optical differences between the white blood cells and the background.
Consequently, a drawback of the conventional video microscope is that it is difficult to make a quantitative analysis of blood cells, and in particular the number of white blood cells.